Carotid endarterectomy is a common vascular surgical procedure that provides a unique opportunity to compare the results of experimental designs that measure treatment efficacy to observational designs that measure treatment effectiveness. While measures of efficacy concern the ultimate performance level achievable for a specific treatment, measures of effectiveness concern the outcomes achieved under everyday conditions. This surgical procedure has been the subject of several recent and comprehensive randomized controlled trials, which are prime examples of measures of efficacy. The effectiveness of the procedure, however, is best measured using administrative databases that provide broad coverage of the total population receiving treatment. This project will build an administrative database that includes the entire cohort of Medicare beneficiaries who received the carotid endarterectomy procedure during the 1989 calendar year. The primary outcome measures in this study are the rates of mortality and morbidity for the period immediately following surgery and the period extending two years after the date of surgery. The analysis will proceed in two stages. First, descriptive information will be developed detailing the short and long term outcomes of the procedure, the distributional patterns of comorbidity, and the range of variation in institutional performance among members of the cohort. Second, the influence of comorbidity and institutional performance upon the short and long term outcomes of the procedure will be assessed. These descriptive and inferential results will then be used to compare the characteristics and results of an administrative data base study to the characteristics and results produced by the existing randomized controlled trials of the carotid endarterectomy procedure.
